The National Institute on Aging (NIA/NIH), Division of Behavioral and Social Research (DBSR) seeks to support efficacy research using Center for Medicare and Medicaid Services (CMS) Medicare Part D data. The Medicare Prescription Drug, Improvement, and Modernization Act of 2003 (MMA) amended the Social Security Act to provide prescription drug benefits to seniors through Medicare (Part D). The implementation of the new prescription drug benefit is the most significant change to the Medicare program since its inception in 1965 and could have profound effects on the health of the elderly. Part D data provide an exceptionally valuable source of data for research on the comparative effectiveness of different drugs for treatment or prevention of a particular condition because the data include information that can be used to address potential biases. Drug plan provider information would allow consideration of such variables and could help to avoid misinterpretations of data. However, without plan information, it would not be possible to determine whether the patients who received each of the drugs being compared were indeed comparable and determine the impact of selection on efficacy. While most researchers can gain access to the majority of CMS Medicare Part D data through standard Data Use Agreements with CMS, the Final Data Rule published by CMS in May 2008 that established guidelines for the distribution of Part D benefit data limits access to plan data to federal agencies and their contractors. The contract will allow researchers, acting to meet the mission of NIA, to conduct valuable analyses on drug efficacy while meeting the guidelines established for appropriate data use by CMS.